Fluorine-containing meltable resin composition

ABSTRACT

An injection moldable fluorine-containing meltable resin composition comprising 70 to 98 wt. % of a fluorine-containing meltable resin, and 2 to 30 wt. % of a needle-shape material having an average diameter of 3 μm or less, an average aspect ratio of between 10 and 100, and Mohs hardness of between 5 and 8, which composition has good sliding and sealing properties and excellent moldability, in particular, moldability of thin wall articles.

FIELD OF THE INVENTION

The present invention relates to a novel fluorine-containing meltableresin composition. In particular, the present invention relates to afluorine-containing meltable resin composition comprising afluorine-containing resin to which a specific needle-shape material iscompounded, having good sliding and sealing properties and being able tobe injection molded, which composition is suitable for dynamic sealingmaterials such as seal rings for automatic transmissions of automobiles,seal rings for hydraulic devices for braking, seals for power steerings,seal rings for CVTs, piston rings for shock absorbers, chip seals forcompressors of air conditioners, valve seals, tubes for push-pullcables, gaskets, and bearings.

PRIOR ART

Hitherto, tetrafluoroethylene polymer compositions containing inorganicor organic fillers for improving dimensional stability, creepresistance, wear resistance and the like are known as materials used forproducing sliding parts for automobiles or industrial equipments.However, the dimensional stability and creep resistance are notsatisfactorily improved by the fillers. Furthermore, these compositionshave a drawback that they cannot be injection molded, and therefore,they have low productivity and are not preferable in view of productioncosts.

For example, in the processing of pistons for shock absorbers, aperipheral surface is shaped in a special form, and a layer ofpolytetrafluoroethylene (PTFE) is wrapped around the peripheral surfaceby press molding and then fusion bonded to prevent the deterioration ofdurability due to twisting of the PTFE resin layer which is caused byrepeated reciprocal movement because of low adhesion between PTFE andthe piston.

Some compositions have been proposed, which comprise injection moldableheat resistant resins and various solid lubricants or for reinforcingmaterials for imparting sliding properties to such the resins orreinforcing them. However, such the compositions have inferior slidingproperties to the tetrafluoroethylene polymer compositions, andfurthermore, they are too stiff to achieve sufficient sealing propertiesin applications where the sealing properties are also required.

With the decrease of weights of various equipments in these years, softmaterials such as aluminum are increasingly used. When such the softmaterials are used as opposite substrates, the above conventional resinmaterials damage the substrates during sliding movement. Furthermore, nocompositions satisfy the sliding properties and other properties whenthey are used in applications which require the high sliding properties,for example, the use at high speed under high load.

JP-A-6-200280 discloses a multilayer sliding part comprising a partsubstrate and a lubricating composition which comprises a fluororesinand zinc oxide whiskers and is impregnated in and coated on thesubstrate. However, this composition uses PTFE having no flowability asa matrix, and cannot be injection molded. In addition, the advantages offillers having tetrapod-form three dimensional shapes represented by thezinc oxide whiskers cannot be attained when they are added to a materialwhich is expected to be used for melt molding.

JP-A-60-120798 discloses a sliding member comprising a fluororesin andsilicon carbide whiskers. The addition of filler having high hardnesssuch as the silicon carbide whiskers can improve the wear resistance ofthe resin composition, but may cause a problem that the compositionwears the substrate over which the sliding member is slid, due to theexcessively increased attacking properties of the composition.

JP-A-5-117475 discloses a resin composition comprising afluorine-containing meltable resin and carbon whiskers (carbon fibers).This composition has several excellent properties and also good slidingproperties because of the inherent sliding properties of the carbonwhiskers having low hardness. However, the sliding properties may bestill insufficient for the applications requiring high slidingproperties such as the use at high speed under high load.

In general, the fluorine-containing meltable resins are said to havelower flowability and less injection moldability than otherthermoplastic resins. Meltable resin compositions comprising thefluorine-containing meltable resin and common fillers tend to formblisters or flow marks on the surface when molded articles have a thinwall, that is, they have low moldability of thin-wall articles.

SUMMARY OF THE INVENTION

The present invention intends to solve the drawbacks of the conventionalfluororesin compositions, in particular, the fluorine-containingmeltable resin compositions and provide a fluorine-containing meltableresin composition which is preferable as a material for sliding partsfor automatic transmissions of automobiles, sliding parts for pistons ofshock absorbers, and various types of seals.

According to the first aspect, the present invention provides aninjection moldable fluorine-containing meltable resin compositioncomprising 70 to 98 wt. % of a fluorine-containing meltable resin, and 2to 30 wt. % of a needle-shape material having an average diameter of 3μm or less, an average aspect ratio of between 10 and 100, and Mohshardness of between 5 and 8.

According to the second aspect, the present invention provide a dynamicsealing material such as a sealing ring for automatic transmissions ofautomobiles, consisting of a molded article of the fluorine-containingmeltable resin composition according to the present invention, or ashock absorber comprising a piston and a piston ring which is placedaround the peripheral surface of the piston wherein the piston ringconsists of a molded article of the fluorine-containing meltable resincomposition according to the present invention.

According to the third aspect, the present invention provide a methodfor producing the above dynamic sealing material.

BRIEF DESCRIPTION OF THE INVENTION

FIG. 1 a schematic view of the gate of a bar flow mold used in Examples.

DETAILED DESCRIPTION OF THE INVENTION

The injection moldable fluorine-containing meltable resin which iscontained in the resin composition of the present invention is wellknown, and its kind is not limit. Preferred examples of thefluorine-containing meltable resin are tetrafluoroethylene-fluoroalkylvinyl ether copolymers (hereinafter referred to as “PFA”),tetrafluoroethylene-hexafluoropropylene copolymers (hereinafter referredto as “FEP”), tetrafluoroethylene-ethylene copolymers (hereinafterreferred to as “ETFE”), polyvinylidene fluoride,polychlorotrifluoroethylene, ethylene-chlorotrifluoroethylenecopolymers, and the like. Among them, PFA, FEP and ETFE are morepreferable in view of the heat resistance, sliding properties,moldability, and the like. In particular, PFA is preferable. Themolecular weight of the fluorine-containing meltable resin is preferablyin the range between 50,000 and 5,000,000.

PFA is a copolymer of tetrafluoroethylene and at least one fluoroalkylvinyl ether of the formula: CF₂═CF—O—Rf wherein Rf is a fluoroalkylgroup having 1 to 10 carbon atoms. Perfluoro(alkyl vinyl ether) ispreferable as the fluoroalkyl vinyl ether. Preferably, PFA comprises 99to 92 wt. % of tetrafluoroethylene and 1 to 8 wt. % of the fluoroalkylvinyl ether.

FEP preferably comprises 99 to 80 wt. % of tetrafluoroethylene and 1 to20 wt. % of hexafluoropropylene.

ETFE preferably comprises 90 to 74 wt. % of tetrafluoroethylene and 10to 26 wt. % of ethylene.

The fluorine-containing meltable resins may comprise other monomerinsofar as the inherent properties of the resin are not impaired.Examples of the other monomers are tetrafluoroethylene (except in thecase of PFA, FEP and ETFE), hexafluoropropylene (except in the case ofFEP), perfluoroalkyl vinyl ethers (except in the case of PFA),perfluoroalkylethylene having 1 to 10 carbon atoms in the alkyl group,perfluoroalkyl aryl ethers having 1 to 10 carbon atoms in the alkylgroup, and compounds of the formula:

CF₂═CF[OCF₂CF(CF₃)]_(n)OCF₂(CF₂)_(p)X

wherein X is a halogen atom, n is a number of 0 to 5 and p is a numberof 0 to 2. The amount of the other monomer is 50 wt. % or less,preferably between 0.01 and 45 wt. % based on the weight of the polymer.

The needle-shape material used in the resin composition of the presentinvention has an average diameter of 3 μm or less, an aspect ratio ofbetween 10 and 100 and a Mohs hardness of between 5 and 8. The materialhaving a Mohs hardness of between 6 and 8 is preferable for effectivelyachieving the effects of the present invention. For example, boratewhiskers such as aluminum borate whiskers and magnesium borate whiskersare used as the needle-shape materials.

When the average diameter of the needle-shape material exceeds 3 μm, itis difficult to mold the composition while maintaining the goodmoldability (moldability of thin-wall articles).

When the aspect ratio is less than 10, the wear resistance isinsufficient, while when the aspect ratio exceeds 100, the anisotropymay appear during molding of thin-wall articles.

When the Mohs hardness exceeds 8, the soft metals may be flawed. Whenthe Mohs hardness is less than 5, the composition may have insufficientstrength under the high load condition under which the composition islubricated with oils, although the composition can be used in theabsence of a lubricant.

In general, the amounts of the fluorine-containing meltable resin andneedle-shape material are between 70 and 98 wt. % and between 2 and 30wt. %, respectively.

When the amount of the needle-shape material is less than 2 wt. %, theimprovement of the strength, heat resistance, dimensional stability andsliding properties are hardly expected. When this amount exceeds 30 wt.%, the moldability of the composition deteriorates, and the moldedarticles having the above properties may not be produced in goodconditions.

The resin composition of the present invention may contain at least oneadditive selected from other inorganic or organic fillers andconventionally used additives in such amounts that the effects of thepresent invention are not impaired. The amount of these additives isbetween 2 and 15 wt. % based on the weight of whole composition.

Examples of the inorganic fillers are as follows:

metals such as stainless steel, iron, nickel, lead, copper, gold,silver, aluminum, molybdenum, rare earth metal, cobalt, boron fibers,etc.;

carbonaceous materials such as carbon black, graphite, carbon fibers,activated carbon, carbon, graphite hollow particles, cokes, etc.;

oxides such as silica, alumina, titanium oxide, iron oxide, zinc oxide,magnesium oxide, tin oxide, antimony oxide, etc.;

hydroxides such as aluminum hydroxide, magnesium hydroxide, etc.;

carbonates such as calcium carbonate, magnesium carbonate, zinccarbonate, etc.;

sulfates such as calcium sulfate, barium sulfate, magnesium sulfate, MOS(fibrous basic magnesium sulfate), etc.;

silicates such as glass, hollow glass particles, glass fibers, talc,mica, kaolin, calcium silicate, wollastonite, xonotlite, PMF (aslug-form fiber. a mixture of calcium aluminosilicate and magnesiumoxide), etc.;

titanates such as potassium titanate, barium titanate, etc.;

nitrides such as aluminum nitride, silicon nitride, etc.;

carbides such as silicon carbides, titanium carbides, etc.;

sulfides such as molybdenum disulfide, molybdenum trisulfide, tungstendisulfide, zinc sulfide, cadmium sulfide, etc.;

phosphates such as calcium phosphate, iron phosphate, etc.;

ferrites such as barium ferrite, calcium ferrite, strontium ferrite,etc.;

The shapes of these inorganic fillers are not limited, and fibrous,needle-shape, powder, granular and beads-shape ones can be used.

The addition of glass or carbon fibers is preferable since thecoefficient of thermal expansion of the composition can be decreased.

The organic fillers are organic materials except fluorine-containingpolymers, which are highly heat resistance, are not decomposed or moltenat temperature at which the resin composition of the present inventionis prepared or at which the composition is processed to produce themolded articles, and can impart mechanical properties, wear resistanceor other functions to the molded articles.

Preferably, the organic fillers are organic materials having a meltingpoint of 400° C. or higher, or a decomposition temperature of 400° C. orhigher when they are non-meltable. Specific examples of the organicfillers are organic fibers such as aramid fibers, polyarylate fibers,phenol resin fibers, etc., and thermosetting resins such as polyimide,phenol resins, condensed polynucleic aromatic (COPNA) resins, etc.

In addition to the above organic fillers, elastomers and so-calledengineering plastics such as polyketones, polyethersulfone,polyphenylenesulfide, liquid crystal polymers, etc. may be exemplified.

The organic fillers may be used independently or in admixture of two ormore of them.

The flowability of the composition can be improved by the addition ofthe liquid crystal polymers.

The amount of these additive resins is between 2 and 10 wt. % based onthe weight of the whole composition.

The above fillers, in particular, the inorganic fillers may be surfacetreated with the following compounds:

aminosilane coupling agents such as γaminopropyl-triethoxysilane(H₂N(CH₂)₃Si(OC₂H₅)₃), m- or p-aminophenyl-triethoxysilane(H₂N—C₆H₄—Si(OC₂H₅)₃), γ-ureidopropyltriethoxy-silane(H₂NCONH(CH₂)₃Si(OC₂H₅)₃),N-(β-aminoethyl)-γ-aminopropyl-trimethoxysilane(H₂N(CH₂)₂NH(CH₂)₃Si(OCH₃)₃),N-(β-aminoethyl)-γ-aminopropylmethyldimethoxysilane(H₂N(CH₂)₂NH(CH₂)₃SiCH₃-(OCH₃)₂), etc.; and organic silane compoundssuch as phenyltrimethoxysilane, phenyltriethoxysilane,p-chlorophenyltrimethoxy-silane, p-bromomethylphenyltrimethoxysilane,diphenyldimethoxy-silane, diphenyldiethoxysilane, diphenylsilanediol,etc.

In some cases, metal soaps such as zinc stearate or other lubricants maybe added to the resin composition to increase the flowability,mold-releasing properties, etc. for facilitating molding. The kinds ofthese lubricants are not limited.

The resin composition of the present invention may be prepared by anyconventional mixing process. For example, the components are mixed witha mixing apparatus such as a twin-cylinder mixer, tumbling mixer,Henschel mixer, and the like, and further mixed and pelletized with amelt kneading apparatus such as a twin-screw extruder.

It is also preferable to prepare a premix of the needle-shape materialand fluorine-containing meltable resin and then mix the premix and othercomponents by the above mixing methods.

The obtained pellets can be molded by any conventional molding methodfor thermoplastic resins such as injection molding, compression molding,extrusion molding, and the like to form articles having a desired shapesuch as plates, films, and the like. The injection molding is preferablefor producing sliding parts at good productivity.

The resin composition of the present invention has good moldability, forexample, moldability of thin wall articles in the insert injectionmolding in which a metal part which constitutes a core is beforehandplaced in a mold and then the fluorine-containing meltable resincomposition is injected in the mold, because of the good flowability ofthe resin composition, and thin-wall sliding parts can be obtained.

EXAMPLES

The present invention will be explained by Examples and ComparativeExamples, which do not limit the scope of the present invention.

Resin compositions prepared in Examples and Comparative Examples wereevaluated by the following test methods:

Raw materials listed in each of Examples and Comparative Examples weremelt kneaded with a twin-screw extruder (LABOPLATOMILL manufactured byTOYO SEIKI Co., Ltd.) at a temperature of between 300 and 370° C., and aresin composition for injection molding was obtained. Then, the resincomposition was supplied into an injection molding equipment (SG 50 MIVmanufactured by SUMITOMO HEAVY INDUSTRIES, LTD.) and subjected to aflowability test using a mold for bar flow molding, and at the sametime, a test piece for a friction and wear test was molded at a cylindertemperature of between 330 and 400° C. and a mold temperature of 200° C.

1. Flowability test

Flowability and appearance were evaluated by injection molding the resincomposition using a mold for bar flow molding.

The shape of the mold gate for bar flow molding is shown in FIG. 1.

Bar flow test conditions:

Cylinder temperature: 320-400° C.

Nozzle temperature: 400° C.

Mold temperature: 200° C.

Injection pressure: 800 kg/cm²

Screw rotation rate: 150 rpm

Injection rate: 2, 5, 8 or 12 mm/min.

2. Friction and wear test

Sliding properties were evaluated using a thrust-type friction and weartester (manufactured by ORIENTEC).

Test conditions for Table 2

Substrate: carburized steel (S45C)

Load: 8 kgf/cm²

Rate: 0.5 m/sec.

Time: 24 hours

Measured items

Friction coefficient

Specific worn amount (unit: cm·s/MPa·m·h)

Test conditions for Table 3

Substrate: carburized steel (S45C)

Load: 4 kgf/cm2

Rate: 0.5 m/sec.

Time: 24 hours

Measured items

Friction coefficient

Specific worn amount (unit: mm³/(km·kgf))

Example 1

92 wt. % NEOFLON PFA AP-201 (manufactured by DAIKIN INDUSTRIES, Ltd.)

8 wt. % Aluminum borate whisker (“ALBOREX” (trade name) manufactured bySHIKOKU CHEMICAL INDUSTRIES, Ltd. average diameter: 1 μm, aspect ratio:30, Mohs hardness: 7)

Example 2

95 wt. % NEOFLON PFA AP-201 (manufactured by DAIKIN INDUSTRIES, Ltd.)

5 wt. % Aluminum borate whisker (“ALBOREX” (trade name) manufactured bySHIKOKU CHEMICAL INDUSTRIES, Ltd. average diameter: 1 μm, aspect ratio:30, Mohs hardness: 7)

Example 3

70 wt. % NEOFLON PFA AP-201 (manufactured by DAIKIN INDUSTRIES, Ltd.)

30 wt. % Aluminum borate whisker (“ALBOREX” (trade name) manufactured bySHIKOKU CHEMICAL INDUSTRIES, Ltd. average diameter: 1 μm, aspect ratio:30, Mohs hardness: 7)

Example 4

92 wt. % NEOFLON PFA AP-201 (manufactured by DAIKIN INDUSTRIES, Ltd.)

8 wt. % Aluminum borate whisker (“ALBOREX” (trade name) manufactured bySHIKOKU CHEMICAL INDUSTRIES, Ltd. average diameter: 1.5 μm, aspectratio: 20, Mohs hardness: 7)

Example 5

92 wt. % NEOFLON PFA AP-201 (manufactured by DAIKIN INDUSTRIES, Ltd.)

8 wt. % Magnesium borate whisker (average diameter: 0.5-1 μm, averagelength: 10-40 μm, Mohs hardness: 7)

Comparative Example 1

92 wt. % NEOFLON PFA AP-201 (manufactured by DAIKIN INDUSTRIES, Ltd.)

8 wt. % Potassium titanate whisker (“TAIBLEX” (trade name) manufacturedby KAWATETSU MINING, Ltd. average diameter: <1 μm, average length: 20μm, Mohs hardness: 4)

Comparative Example 2

95 wt. % NEOFLON PFA AP-201 (manufactured by DAIKIN INDUSTRIES, Ltd.)

1 0 5 wt. % PAN carbon fiber (“TORAYCA” (trade name) manufactured byTORAY. average diameter: 7 μm, aspect ratio: 10)

Comparative Example 3

95 wt. % NEOFLON PFA AP-201 (manufactured by DAIKIN INDUSTRIES, Ltd.)

5 wt. % Pitch carbon fiber (“KURECA” (trade name) manufactured by KUREHACHEMICAL INDUSTRIES, Ltd. average diameter: 14.5 μm, aspect ratio: 20)

Comparative Example 4

92 wt. % NEOFLON PFA AP-201 (manufactured by DAIKIN INDUSTRIES, Ltd.)

8 wt. % Aluminum borate (“ALBORITE” (trade name) manufactured by SHIKOKUCHEMICAL CORPORATION, Ltd. average particle size: 3 μm, Mohs hardness:7)

Comparative Example 5

92 wt. % NEOFLON PFA AP-201 (manufactured by DAIKIN INDUSTRIES, Ltd.)

8 wt. % Magnesium borate (average particle size: 3 μm, Mohs hardness: 7)

Comparative Example 6

91 wt. % NEOFLON PFA AP-201 (manufactured by DAIKIN INDUSTRIES, Ltd.)

9 wt. % Silicon carbide whisker (“TOKA WHISKER” (trade name)manufactured by TOKAI CARBON Co., Ltd. average diameter: 0.3-0.6 μm,average length: 5-15 μm, Mohs hardness: 9)

Comparative Example 7

85 wt. % NEOFLON PFA AP-201 (manufactured by DAIKIN INDUSTRIES, Ltd.)

15 wt. % Zinc oxide whisker (“PANATETRA” (trade name) manufactured byMATSUSHITA AMTEC. average diameter: 0.2-3.0 μm, average length: 2-50 μm,Mohs hardness: 4)

Comparative Example 8

92 wt. % NEOFLON PFA AP-201 (manufactured by DAIKIN INDUSTRIES, Ltd.)

8 wt. % Calcium carbonate whisker (“WHISCAL” (trade name) manufacturedby SHIKOKU CHEMICAL CORPORATION, Ltd. average diameter: 0.5-1.0 μm,average length 20-30 μm, Mohs hardness: 3.5-4)

The results of the flowability test and friction and wear test are shownin Tables 1, 2 and 3, respectively.

TABLE 1 Injection Bar flow rate length Surface (mm/sec.) (mm) conditionsEx. 1 2  31 5 103 Good surface 8 120 Vertical wrinkles 12  127 Surfaceroughness Comp. 2  30 Flow marks, warped Ex. 1 5 105 Flow marks, bubbles8 117 Flow marks, bubbles, skin layer 12  123 Surface roughness,hairiness, bubbles Comp. 2  30 Tip end disordered Ex. 3 5 115 Flowmarks, bubbles, silver streaks 8 133 Flow marks, silver streaks, a fewbubbles 12  138 Flow marks, silver streaks, a few bubbles, verticalwrinkles

TABLE 2 Friction Wear Rate coefficient (cm · s/MPa · m · h) Example 10.17-0.23 8.3 × 10⁻⁶ Comp. Ex. 2 0.17-0.23 2.1 × 10⁻⁴

TABLE 3 Friction Specific coefficient Wear rate Note Ex. 1 0.20-0.24 4.9× 10⁻² Ex. 2 0.19-0.24 6.7 × 10⁻² Ex. 3 0.15-0.19 3.8 × 10⁻² Ex. 40.26-0.30 2.9 × 10⁻² Ex. 5 0.24-0.28 4.2 × 10⁻² C. Ex. 1 0.26-0.34 4.9 ×10⁻² Large fluctuation of friction coefficient C. Ex. 4 0.26-0.36 8.1 ×10⁻² Large fluctuation of friction coefficient C. Ex. 5 0.43-0.51 6.5 ×10⁻² Large fluctuation of friction coefficient C. Ex. 6 0.20-0.22 9.5 ×10⁻² Against Worn C. Ex. 7 Melting Melting wearing wearing C. Ex. 8Melting Melting Bubbled during molding wearing wearing

From the results in Table 1, it is understood that the composition ofComparative Example 1 or the compositions containing the carbon fiberhaving the large average diameter and the like had inferior moldabilityof thin wall articles.

From the results of Table 2, it is understood that the slidingproperties of the carbon fiber which is conventionally used forimparting sliding properties has the inferior sliding properties to thespecific needle-shape materials used according to the present invention.

From the results of Table 3, it is understood that, although thecomponents were used at the same volume ratios in Examples 1, 4 and 5and Comparative Examples 1 and 4-8, the composition of ComparativeExample 1 suffered from the large fluctuation of friction coefficientand the compositions of Comparative Examples 4 and 5 had low wearresistance and suffered from large fluctuation of friction coefficientbecause the fillers were granular. Furthermore, the composition ofComparative Example 6 flawed the substrate and therefore its ownspecific wear rate increased. The compositions of Comparative Examples 7and 8 suffered from abrupt wearing and were melting worn.

Effects of the Invention

The present invention provides a fluorine-containing meltable resincomposition which has the good sliding and sealing properties requiredfor the sliding parts used in the automobile and industrial equipmentfields, in particular, the sliding and sealing properties at high speedunder high load, and also excellent moldability, in particular,moldability of thin wall articles.

What is claimed is:
 1. An article of manufacture, comprising: a slidingpart; and a sealing ring placed around a peripheral surface of saidsliding part, said sealing ring being made of a fluorine-containingmeltable resin composition comprising: 70 to 98 wt. % of afluorine-containing meltable resin, and 2 to 30 wt. % of a needle-shapematerial having an average diameter of 3 μm or less, an average aspectratio of between 10 and 100, and Mohs hardness of between 6 and
 8. 2.The article of manufacture according to claim 1, wherein saidneedle-shape material is a borate whisker.
 3. The article of manufactureaccording to claim 2, wherein said borate whisker is an aluminum boratewhisker.
 4. The article of manufacture according to claim 2, whereinsaid borate whisker is a magnesium borate whisker.
 5. The article ofmanufacture according to claim 1, wherein said fluorine-containingmeltable resin is a tetrafluoroethylene-fluoroalkyl vinyl ethercopolymer, a tetrafluoroethylene-hexafluro-propylene copolymer of anethylene-tetrafluoroethylene copolymer.
 6. The article of manufactureaccording to claim 1, wherein said article of manufacture is a shockabsorber.
 7. The article of manufacture according to claim 1, whereinsaid article of manufacture is a power steering device.
 8. The articleof manufacture according to claim 1, wherein said article of manufactureis an automatic transmission.
 9. The article of manufacture according toclaim 1, wherein said article of manufacture is a constant velocityjoint.
 10. The article of manufacture according to claim 1, wherein saidarticle of manufacture is a hydraulic device for braking.
 11. Thearticle of manufacture according to claim 1, wherein said article ofmanufacture is a compressor for air conditioners.
 12. A method of makinga sealing ring for an article of manufacture, comprising: providing afluorine-containing meltable resin composition comprising: 70 to 98 wt.% of a fluorine-containing meltable resin, and 2 to 30 wt. % of aneedle-shape material having an average diameter of 3 μm or less, anaverage aspect ratio of between 10 and 100, and Mohs hardness of between6 and 8; and forming a sealing ring from said composition by injectionmolding of said composition in an injection molding machine.
 13. Themethod of making a sealing ring according to claim 12, wherein saidneedle-shape material is a borate whisker.
 14. The method of making asealing ring according to claim 13, wherein said borate whisker is analuminum borate whisker.
 15. The method of making a sealing ringaccording to claim 13, wherein said borate whisker is a magnesium boratewhisker.
 16. The method of making a sealing ring according to claim 12,wherein said fluorine-containing meltable resin is atetrafluoroethylene-fluoroalkyl vinyl ether copolymer, atetrafluoroethylene-hexafluro-propylene copolymer or anethylene-tetrafluoroethylene copolymer.